The present invention relates to a simplified process for forming an adhesive layer on a release liner for application of the adhesive to a base member. More particularly, it relates to a paper-backed release film useful in said process.
In many applications, adhesives are applied to a base member as a pre-formed film which is carried on a polymeric release liner. Due to the nature of the adhesives required in many of these applications, the adhesive layer cannot be formed directly on the release liner. Many adhesives are extrusion coated and/or cured at elevated temperatures at which the release liners, which are usually thermoplastic, are not dimensionally stable. At the elevated temperatures used to extrude and/or cure the adhesives, the release liner softens and stretches under the weight of the adhesive.
Currently in applications requiring the combination of a polymeric release liner and heat treated adhesives, the adhesive is coated onto a release paper and laminated to the film which functions as the release liner. The paper provides the necessary supporting substructure during the coating and curing of the adhesive. The release paper-adhesive-release liner composite is wound into a roll which may be stored until application to a base member whereupon the release paper is removed and the adhesive layer with the release liner is assembled with the base member in a transfer laminating operation.
U.S. Pat. No. 3,509,991 to Hurst teaches a release sheet and an adhesive structure embodying the same. This reference addresses the problem which occurs in marketing adhesive tape in roll form, i.e., the non-backed adhesive sticks to the backside of the tape already in roll form. The problem is overcome by providing a release sheet with different release values on each side. The release sheet comprises a sheet of paper which is extrusion coated with polyethylene and then both sides are coated with a release agent. Pressure sensitive adhesive is then applied to the surface with the more difficult release properties and the resulting laminate is wound into roll form. When pulling the laminate from the roll, the adhesive sticks to the surface having the more difficult release properties rather than to the backside of the tape already on the roll. When the tape is used, the adhesive is applied to a desired surface, and the film-paper laminate is removed from the adhesive. The reference teaches that the polyolefin film and paper layer are firmly bonded to each other.
U.S. Pat. No. 4,398,985 to Eagon teaches a releasable self-detackifying laminate construction. The reference addresses the problem that once the paper stock is peeled off a laminate, a tacky pressure sensitive adhesive surface is exposed on the base stock. This tackiness makes further processing of the base stock by automated equipment next to impossible. The reference overcomes the problem by coating a film of a non-silicone containing polymer onto one side of the paper stock and then laminating this construction to an adhesive which has been coated onto a release liner. When the paper stock is peeled away, the polymer film will delaminate from the paper stock and be permanently affixed to the adhesive coating. The resulting substrate has a detackified adhesive surface which can be further used or processed either by hand or by automated equipment.